Electric shavers

ABSTRACT

A dry shaver comprising a cutter guided for reciprocating movement along a substantially linear path by means of at least two resilient members extending generally perpendicular to said path, each resilient member comprising a stem and at least two legs projecting from one end of the stem in continuation thereof, the free end of at least one leg being secured to the cutter and the free end of at least one other leg being secured to a fixed part of the shaver, and the free end of the stem being restrained against vibration in the direction parallel to the path of reciprocation of the cutter.

United States Patent Wellinger Aug. 27, 1974 [541 ELECTRIC SHAVERS FOREIGN PATENTS OR APPLICATIONS lnventori Roger Paul Welling", Neuchalel, 385,670- 3/1965 Switzerland 30/4392 Switzerland [73] Assignee: The Gillette Company, Boston, Primary EXuNlirwrAl Lawrence Smith Mass. I Assistant Examiner-Gary L. Smith Wed: y 20, 1972 Attorney, Agent, or Firm-Flynn & Frrshauf [Zl Appl. NCLZ 273,478 ABSTRACT A dry shaver comprising a cutter guided for reciprol l Foreign Apphcatlo" P 0 Dam cating movement along a substantially linear path by July 27, I971 Great Britain I. 35176/71 means of at least two resilient members extending generally perpendicular to said path, each resilient mem- [52] US. Cl. ..l 30/4392 bercomprising a stem and at least two legs projecting [51 Int. Cl B26b 19/02 from one end of the stem in continuation thereof, the [58] Field of Search 30/438, 43.9, 43.91, 43.92, free end of at least one leg being secured to the cutter 30/3465] and the free end of at least one other leg being secured to a fixed part of the shaver, and the free end of [56] References Cited the stem being restrained against vibration in the di- UNITED STATES PATENTS rection parallel to the path of reciprocation of the cut- 7 3,290,777 12/1966 Jepson 30 4392 3,365,796 l/l968 Tolmie I 30/4392 7 Claims, 4 Drawing Figures 3,504,433 4/1970 Futterer 30/4392 *2 HL 23a E722 8 9 i ia PAIENTEU M1627 I974 33, 831 .273 SHEET 20F 2 ELECTRIC SHAVERS This invention relates to dry shavers for shaving hair from human skin. The power consumption of dry shavers is an important factor in that it determines the length of battery life, or recharging frequency, in battery powered shavers and, in all types, has an influence on the desired power and hence weight and bulk of the drive motor to be used.

One of the factors influencing power consumption is the power absorbed in the bearings or support structure on which the moving cutter or cutters of the shaver are mounted. Frictional forces should be reduced as far as possible.

Where a moving cutter is intended to move along a substantially linear path, as is commonly requiredin' known types of razors, it is also desirable for the bearings or support structure to guide the cutter along a.

path which is as accurately linear as possible.

In an endeavour to achieve these objects, it has been proposed in British Patent Specification No. 1,129,656

corresponding to US. Pat. No. 3,504,433 to mount thecutter on a pair of spaced apart resilientplates having.

three coplanar legs joined at their roots. The free ends of the two outer legs are secured to the shaver body and the free end of the middle leg is securedto a stage carrying the cutter. However, in this proposal, the other end of each resilient member, where the legs are joined, is free to vibrate in sympathy with the cutter, and can develop high amplitude vibrations as a result. This is disadvantageous in that the stability of reciprocation of the cutteris adversely affected, and in that undesirable vibration is passed on to the shaver body and undesirable noise is generated.

SUMMARY OF THE lNVENTlONv The dry shaver according to the present invention comprises a cutter guided for reciprocating movement along a substantially linear path by means of at least two resilient members extending generally perpendicular to said path, each resilient member comprisinga stem and at least two legs projecting .from one end of the stem in continuation thereof, the free end of at least one leg being secured to the cutter and the free end of at lest one other leg being secured to a fixed part of the shaver, and the free end of the stem being restrained against vibration in the direction parallel to the path of reciprocation of the cutter.

In the known construction employing resilient members with a plurality of legs but no stem which is restrained, we have found that the common end or root end of the legs, which is not secured either to the body of the shaver or to the movable cutter, tends to develop a very large amplitude of vibration, greater than that of the cutter itself. This is not desirable, for reasons mentioned above, and is substantially reduced by the present invention. The root ends of the legs vibrates with an amplitude substantially less than that of the cutter itself.

The present invention is not concerned with the exact nature of the cutting head of a shaver, but is especially valuable in the type of cutting head which consists of a stationary outer foil which is perforated and curved and an inner cutter which comprises a plurality of blades mounted on a carrier, the blades being profiled so as to match the curvature of the foil, and the inner cutter being oscillated along'a substantially linear of resilient material, one on each side of the.stem,.in. generally opposed relationship in the directionof the path of movement of the cutter, and;mounted.on a fixed partof the shaver. Alternatively, the restraining means may comprise a leaf spring extending transversely to the stem between said stem and a fixed part of the shaver.

In an embodiment which will be describedbelow, each resilient member has three coplanar legs, the free ends of the middle leg being mounted, on a fixed part of the shaver and the cutter being mounted on the free, ends of the two outer legs.

Each resilient member is preferably in the form of a resilientplate formed with three legs. Theplate. may be of metal and each legmay be stiffened byan upturned.

flange along one or more edges thereof. Furthermore, it may be ensured that the legs carrying the cutter and the stem flex together by. providing-an upturned flange. running along the outer edge of each outer legand continuing along the edge of the stem.

Because of the resilient mounting, the cutter has-a natural frequency of vibration with thecutter oscillating along said linear path. Means are preferably provided operable to drive said cutter at or close to said resonant frequency. However, it will be appreciated that the low friction and linear motion of the, present invention are obtained without resonant operation, and in some instances it may be preferred to operate. the

driving means at a frequency different to but bearing a selected relationship to saidmaterial frequency.

The dry shaver may also comprise one or more counterweights in the vicinity of the cutter and oscillatable along a substantially linear path substantially parallel with that of the cutter, the counterweights being supported by a supporting structure similar to that. supporting the oscillatable cutter, the means operable to drive the cutter being also operable to drive the counterweights in antiphase with the cutter. This arrange.- ment substantially reduces vibration whichis otherwise caused by the mass of the oscillating cutter.

It is desirable for the counterweight or counterweights to be mounted as close to the moving cutter as possible in order to minimise the small vibrational mo,- ment which occurs when their massesoscillate in antiphase along different axes.

Alternatively, a. two-part cutter may be employed, the two cutter parts being respectively driven in antiphase.

Preferably, the cutter or cutter part supporting structure, and/or the counterweight supporting structure, include two resilient members spaced apart in the direction of the path of movement of the cutter and/orcounterweight respectively.

The exact nature of the driving means or power source used is not critical but where resonance is re-' quired andthe shaver is intended for operation from AC mains then a synchronous AC motor may be used.

This will run always at a constant speed determined by the mains frequency and so it will be able to drive the resonant cutter and counterweight system at their resonant frequency using a cam arrangement such as is described below, provided they are tuned to resonate at the appropriate frequency.

Alternatively, a DC rotary motor may be employed, fed either from batteries contained in the shaver casing or from a rectifier circuit fed from the mains. A constant speed can be obtained from a DC motor relatively simply using a back-EMF bridge in association with a power control amplifier system. Alternatively, a servotype system can be used in which a tachometer generator is driven by the motor and its output voltage, proportional to the motor speed, is compared with a reference to provide an error signal for controlling the motor input current. When the motor is thus run at a constant speed and resonant operation is desired, it is necessary simply to arrange the resonant system or systems of the shaver to match the speed of the motor. This may be done initially in an approximate fashion and a variable element may be included so that the motor speed can be varied over a range and can be manually adjusted within the range to achieve resonance of the cutter and/or counterweight system.

Yet again, it is possible to employ driving means in the form of a vibratory motor having a two part reactive system constituted by a permanent magnet and a coil which can be supplied with current to produce vibratory movement of one part of the system relative to the other.

In order that the invention may be more clearly understood, some preferred embodiments thereof will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

FIG. I is a cross-section, taken on line I-I in FIG. 2, showing the main parts of one electric shaver according to the invention;

FIG. 2 is a cross-section taken on line IIII of FIG. 1;

FIG. 3 shows a resilient member from the shaver shown in FIGS. 1 and 2; and

FIG. 4 illustrates the operation of a resilient suspension system such as is shown in FIGS. 1 and 2.

Referring to FIG. 1, an inner movable cutter of the dry shaver is shown at 1. Of course, this will be associated with a stationary outer cutter, which may be a perforated foil, but since this forms no part of the present invention it is not illustrated, and neither is the surrounding casing with which the shaver would be normally provided.

The cutter l is to be oscillated along a substantially linear path in the direction of its length.

The cutter l is supported on a cutter supporting structure which includes a mounting block 2 on which the cutter l is secured, possibly with the interposition of some resilient means such as one or more springs, or rubber. The mounting block 2 is mounted directly on a bridge .3 which, at both ends, is bifurcated in the same manner as the bridge 3a, which is shown in FIG. 2 and which will be further referred to below. The two downwardly projecting portions at the left hand end of bridge 3 are securely fixed, for example by rivets, to the upper ends of the two outer legs 4 and 5 (see FIG. 3) of a resilient member 6. The resilient member 6 is shown in perspective in FIG. 3 but in longitudinal cross-section in FIG. 1. A transverse cross-section of resilient member 6 is seen in FIG. 2.

The resilient member 6 extends generally perpendicular to the path of oscillation of the cutter l. A third and middle leg 7 of resilient member 6 is situated between the legs 4 and 5 and the upper end of leg 7 is secured, for example by rivets or screws, to a fixed part 8 of the shaver. The fixed part 8 may form part of a chassis carrying the working parts of the shaver within a suitable casing.

FIG. 1 shows in full only one side of the structure but this will in practice be symmetrical so that the left hand side of the structure, as shown in FIG. 1, would he duplicated in mirror image on the right hand side.

Thus, the cutter l is supported in the shaver by means of two resilient members 6, one at each end of the bridge 3.

A pair of counterweights 9 are fixedly mounted on the bridge 3a which is similar to, but shorter than, the bridge 3 and bridge 3a is supported at its ends by two resilient members a (of which only the left hand one is shown in FIG. 1) which are generally similar in form to the resilient member 6.

In FIGSS. l and 2 the centre leg of resilient member 6a, numbered 7a, is shown secured to the fixed portion 8 of the shaver. The two outer legs 4a and 5a are secured to the two downwardly projecting portions 10a at the end of the bridge 3a.

The resilient members 6 and 6a are of equal lengths but members 6 are set slightly higher than members 6a so that bridge 3 lies above bridge 3a. The counterweights 9 lie between the two bridges and are thus situated quite close to the movable cutter 1.

Referring to FIG. 3, the resilient member 6 has a stem extending away from the roots of the three legs 4, 5 and 7 in the opposite direction to said legs, the stem being indicated at 11. In FIG. 1 it can be seen that the stem 11 is restrained at a point remote from the roots of the legs by means of prism-shaped blocks 12 of deformable material, such as soft rubber, these blocks being mounted on plates 13 which in turn are fixed to a portion 14 of the shaver. A corresponding extension Ila of resilient member 6a is similarly restrained by deformable blocks 12a of which one is mounted on the central plate 13 and the other on a further plate 130.

FIG. 4 shows diagrammatically the bridge 3 and its supporting structure including the two resilient members 6. The members 6 are shown in full lines in their central position, in which position they are illustrated in FIG. 1, and in broken lines in positions displaced to either side of the central position. As the bridge 3 is displaced to either side of its central position the fixed central legs 7 of members 6 are flexed out of the general plane of the members 6, whereas the outer legs 4 and 5 and the stems ll flex together, remaining in approximately the same plane.

The type of suspension shown in FIG. 4 can be arranged to produce a precisely linear path of displacement for the bridge 3. The fact that the portions 8 to which the central legs 7 are fixed may not be in the same plane as the bridge 3 may be compensated for by suitably selecting the relative flexibilities of the central leg 7 and the combination of the two outer legs 4 and 5.

As the bridge 3 is moved from side to side along its linear path the lower end of the stem 11 of each resilient member moves slightly in a direction perpendicular to the bridge 3. This movement is permitted by the deformability of the restraining blocks 12, while uncontrolled oscillation of the stem 11 in the direction parallel to bridge 3 is prevented. By virtue of the resilience of the members 6, the cutter 1, bridge 3 and the members 6 themselves will have a natural resonant frequency of vibration, with the cutter l oscillating along a linear path parallel with that of the bridge 3. The fre quency will be determined by the mass of the cutter l and bridge 3 and the stiffness of the resilient members 6.

The members 6 may be made of thin sheet metal plate, for example of copper/beryllium alloy or steel. To raise the natural resonant frequency in the embodiment described, the members 6 are stiffened and this prevents unwanted oscillations. This is achieved by means of upturned flanges 17 along the two side edges of the central leg 7 and further upturned flanges 18 which run along the outer edge of each of the outer legs 4 and 5 and continue along the outer edges of the stem 11. Besides making the member 6 stiffer overall, the flanges 18 also ensure that the stem 11 and outer legs 4 and 5 flex together and that the central leg 7 flexes separately therefrom. This is important, because if the central leg 7 and the stem 11 were stiffened as a single unit, for example by means of a single central reinforcing member, they would stay substantially straight as the bridge 3 oscillates from side to side, because both the central leg 7 and the stem 11 are fixed or restrained. Then, the legs 4 and 5 would simply flex from side to side about approximately the centre of the member 6 and their upper ends would execute an arcuate motion having a small undesired component perpendicular to the bridge 3.

The bridge 3a supporting counterweights 9 can oscillate in the same manner as bridge 3, as described with reference to FIG. 4, on its supporting resilient members 6a. The mass of the counterweights 9 is selected so that when they oscillate in antiphase to and parallel to the cutter l, the resultant vibration is substantially zero. The natural frequency of the counterweights 9 on their supporting structure may be tuned to be equal to that of the cutter l by suitably selecting or-adjusting the stiffness of the resilient members 6a in relation to the mass of the counterweights 9 and bridge 3a.

In the embodiment shown, the flanges 17a on member 6a extend slightly further upwards than the flanges 180, the upper end of which is shown by the broken line in FIG. 1.

Referring again to FIG. 1, the driving means for the cutter l is shown in this embodiment as an electric rotary motor 19 mounted on a fixed portion 20 of the shaver. The output shaft 21 of the motor passes through respective apertures 22 and 22a in the bridge 3 and the bridge 3a and located within these apertures and fixedly mounted on shaft 21 there are eccentric cams 23 and 230 respectively. The cams 23 and 23a are arranged to be 180 out of phase so that as the motor 19 rotates the bridges 3 and 3a are caused to oscillate along their linear paths in antiphase, thus producing the desired vibration-free operation.

This will also be achieved if, the motor 19 is not run at such a speed as to drive the cutter l and counterweights 9 at their resonance frequency.

However, in order to drive them at their natural resonance frequency, or a frequency close thereto, the

motor 19 must be controlled to the appropriate speed. Control circuitry suitable for achieving this in a DC motor has already been referred to and such circuitry is well known. It will therefore not be described in detail herein.

The bridges 3 and 3a could alternatively be driven by a vibratory motor having a two part reactive system comprising a permanent magnet and a coil supplied with alternating current or a train of current pulses derived from a battery. The coil can be mounted on one bridge and the coil on the other.

It will be appreciated that, using the three-armed rcsilient members of FIG. 3, the two outer legs 4 and 5 could be secured to fixed portions of the shaver and the bridge 3 could be carried on the central leg 7. In that case, if stiffening of the resilient member is necessary, it would be done by reinforcement extending along'the centre leg 7 and the stem 11 and separate reinforcement of the two legs 4 and 5 so that the latter two legs could flex out of the general plane of the resilient element.

It will be apparent to one skilled in the art that the resilient elements could alternatively be formed from metal wire or from a suitable plastics material and also that they could be formed integrally with the bridges 3 u and 3a.

Resilient members as shown in FIGS. 1 to 4 enable the movement of the cutter, and of the counterweight when present, to be made very precisely linear, with very low friction, at the same time substantially eliminating unwanted vibration, as occurs without provision of the restrained stem. This form of cutter supporting structure is also free from the problems which can otherwise be caused by dust and dirt entering the shaver.

The use of a counterweight or counterweights oscillating in antiphase to the cutter also assists in achieving low vibration when the shaver is operated. Resonant operation of the cutter, and also of the counterweight when present, is found to reduce power consumption.

In place of the counterweight, the cutter could be formed in two parts, being longitudinally split for example, and the two cutter parts could be reciprocated in antiphase.

A feature of the resilient supporting members as have been described is that they perform the combined functions of supporting, guiding along a substantially linear path, and applying a resilient bias towards the rest position.

I claim:

1. A dry shaver comprising:

a cutter movable in reciprocating movement along a substantially linear path;

at least two resilient members extending generally perpendicular to said path to guide the cutter in its linear reciprocating movement, each resilient member comprising a stem portion having first and second ends and at least two legs projecting from the first'end of the stem in continuation thereof, the free end of at least one leg being secured to the cutter and the free end of at, least one leg being secured to'a fixed part of the shaver; and restraining means for restraining the second end of the stem against movement in the direction parallel to the path of reciprocation of the cutter while permitting said second end of the stem a limited degree of freedom of movement in a direction perpendicular to the path of reciprocation of the cutter when the cutter is moved along said linear path.

2. A dry shaver according to claim 1, wherein said restraining means comprises elements of resilient material, one on each side of the stem near the second end of the stem, in generally opposed relationship in the direction of the path of movement of the cutter, and mounted on a fixed part of the shaver.

3. A dry shaver according to claim 1, wherein each resilient member has three legs which are coplanar in the natural rest position of the member, the middle leg being secured to a fixed part of the shaver and the two outer legs being secured to the cutter.

4. A dry shaver according to claim 3, wherein each of said resilient members is in the form of a flat plate stiffened with upturned flanges along the outer edges of the respective outer legs thereof, said flanges being continued along the outer edge of the portion of the stem from which said legs project.

5. A dry shaver according to claim 1, wherein the cutter is formed in two parts reciprocable in antiphase, each cutter part being mounted by means of at least two of said resilient members.

6. A dry shaver according to claim 1, wherein the shaver includes a counterweight reciprocable in antiphase to the cutter, the counterweight being mounted by means of at least two said resilient members.

7. A dry shaver according to claim 1, comprising driving means including a rotary motor and cam, said rotary motor producing said reciprocatory movement through the intermediary of said cam. 

1. A dry shaver comprising: a cutter movable in reciprocating movement along a substantially linear path; at least two resilient members extending generally perpendicular to said path to guide the cutter in its linear reciprocating movement, each resilient member comprising a stem portion having first and second ends and at least two legs projecting from the first end of the stem in continuation thereof, the free end of at least one leg being secured to the cutter and the free end of at least one leg being secured to a fixed part of the shaver; and restraining means for restraining the second end of the stem against movement in the direction parallel to the path of reciprocation of the cutter while permitting said second end of the stem a limited degree of freedom of movement in a direction perpendicular to the path of reciprocation of the cutter when the cutter is moved along said linear path.
 2. A dry shaver according to claim 1, wherein said restraining means comprises elements of resilient material, one on each side of the stem near the second end of the stem, in generally opposed relationship in the direction of the path of movement of the cutter, and mounted on a fixed part of the shaver.
 3. A dry shaver according to claim 1, wherein each resilient member has three legs which are coplanar in the natural rest position of the member, the middle leg being secured to a fixed part of the shaver and the two outer legs being secured to the cutter.
 4. A dry shaver according to claim 3, wherein each of said resilient members is in the form of a flat plate stiffened with upturned flanges along the outer edges of the respective outer legs thereof, said flanges being continued along the outer edge of the portion of the stem from which said legs project.
 5. A dry shaver according to claim 1, wherein the cutter is formed in two parts reciprocable in antiphase, each cutter part being mounted by means of at least two of said resilient members.
 6. A dry shaver according to claim 1, wherein the shaver includes a counterweight reciprocable in antiphase to the cutter, the counterweight being mounted by means of at least two said resilient members.
 7. A dry shaver according to claim 1, comprising driving means including a rotary motor and cam, said rotary motor producing said reciprocatory movement through the intermediary of said cam. 